The serial number of a Cartier watch can be located on the back of the watch face piece, typically etched into the surface of the watch itself. It is usually located near the model number. The serial number helps to provide a record of the source and authenticity of the watch.
Cartier watches that do not contain a serial number, or watches that have a removed or damaged serial number, may not be authentic to the Cartier brand. It is important for a Cartier watch to have an intact serial number in order to benefit from Cartier's International Guarantee and Limited Warranty.